towell miter part III: front plate and bridge

This entry will cover the remaining steps that need to be accomplished prior to bending the sidewalls. The front plate needs to be fabricated, and the dovetails cut for joining it to the sidewalls, and the bridge needs to be completed to the point of fitting the tenons to the sidewalls. After that, its simply a matter of cleaning the interior surfaces, and then I’ll make the bend.

Front plate

This is a pretty self-explanatory process – first I need to cut the plate to size, then cut the dovetail joints to fit it to the sidewalls. The sizing of the plate is fairly straightforward – it’s the height of the sidewall pieces above the dovetails – in this case, the sidewall stock is 2″ wide, minus 5/16″ for the sole, and another 1/16″ for peining material. So the remainder is 1-5/8″ tall (I measure the piece itself as a check). In width, the plate needs 2-1/8″ for the interior of the plane, with 2 x 3/16″ for each sidewall, and an additional 1/8″ for peining material on either side – this gives me a width of 2-5/8″.

Once the plate is cut, I need to clean up the cuts from the hacksaw. I used to do this work with files, but I find I get results that are as good (and much quicker) with a good 12″ disc sander:

With the plate square, it’s a simple matter to mark of the ‘tails’ that will join the front plate to the sidewalls. This joint is responsible for holding the bend in place, and experiences some fairly good lateral stress, so I feel that tails on the front piece are really the only sensible choice here. At any rate, I’m going to include less and less ‘cut’ and ‘file’ pictures, but I’ll still include them occasionally. Here are the dovetails being cut:

and then they’re filed. Flip the plate and repeat. Next, mark the ‘pins’ from this piece at either end of the sidewall stock… pay close attention to the orientation that will result after the bend – there is nothing more frustrating than cutting a perfect dovetail that is flared in the wrong direction, scrapping a sidewall piece you’ve already got a half-dozen or so hours into… or so I’ve been led to believe.

Here’s the fit of one side. Ideally, you want this fit tight enough that it requires some light hammer taps to seat or remove the piece – that makes for very easy peining later on. In reality, you can get away with a good bit more slop than that, but it’s a lot more work later…

The only thing remaining is filing secondary dovetails. These dovetails are done in 3/16″ stock – not nearly as thick as the sole – so I’ll use a ‘conventional’ full-depth taper for them. Here they are marked out:

and filed:

At this point, all of the operations on the sidewall pieces are complete, except cleaning up the interior surface. It is all but impossible to adequately clean up the inside of an already-assembled plane, so I want to put a final finish on the inside now. I use PSA sandpaper on a large granite block for this – and for the interior I’ll sand to 220 grit. You can go higher than this if you prefer bright and shiny, but I I like a little texture to steel. The finer you abrade the steel, the more fingerprints and dirt will stand out and interfere with the surface aesthetics, so bear that in mind if you wish to use a higher grit for your surfaces… I will say that almost without exception, I have tended to back off on my surface treatments over time – I’ve rarely, if ever, felt I needed to shift my regimen to a higher degree of polish. This is largely a matter of taste, though, so use the finish that suits your sensibilities.

Here is the sidewall, now with all the cutting and filing completed, and ready for the bending operation:

But before I actually do the bend, there’s just one more task I want to finish.

Bridge tenons

It is infinitely easier to fit the bridge tenons before bending the sidewalls, so I cut the bridge piece from 5/16″ stock, and cut/file the tenons in place. I will finish the actual shaping of the bridge a bit later, but for now I want to get the fit for the bridge correct before I bend the sidewalls up. The tenons themselves are really straightforward – cut, remove some metal, file a bit and – voilá! The only tricky part of this exercise is filing the shoulder in place on the tenons. Once I’ve got the tenons themselves cut I have to remove about 1/16″ of material from the top face of each . This gives a nice shoulder, and a substantially nicer aesthetic fit to the bridge when the plane is completed. Here’s one side of the bridge, ready for the shoulder operation:

What I’ll do is use the vise jaws as a guide to cut to depth with my hacksaw – this will make it much easier to get the filing depth correct in a minute. I’m careful not to cut deeper than my 1/16″ depth, as cutting beyond that point will substantially reduce the strength of the tenons:

Once the cut is made, I use the jaws again as a guide, this time for a pillar file used horizontally to remove the face material from the tenons ( you can’t actually see the tenons behind the file, but trust me – they’re there.)

Once you’ve gotten to depth, flip the bridge and repeat on the other side. A few test fits and refinements, and you’re left with the bridge piece looking something like this:

Be certain you have a perfect test fit on either side of the sidewall piece (and pay very close attention to orientation). You want a fit that is easily pressed in place without much resistance, but not too sloppy – you must be able to get the bridge in place after the bending operation without too much trouble. Here is one side’s test fit:

And now I’m finally ready for the nervewracking step of bending the sidewalls. I find everything prior to the sidewalls is accompanied by a silent prayer that the bend goes off well – it’s not unheard of for a bad bend to mean all of the work to this point is basically scrap metal, so there is a bit of apprehension in building up to it.